307 lines
11 KiB
C++
307 lines
11 KiB
C++
// © 2016 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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// Copyright (C) 2009-2012, International Business Machines
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// Corporation and others. All Rights Reserved.
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//
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// Copyright 2007 Google Inc. All Rights Reserved.
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// Author: sanjay@google.com (Sanjay Ghemawat)
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//
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// Abstract interface that consumes a sequence of bytes (ByteSink).
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//
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// Used so that we can write a single piece of code that can operate
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// on a variety of output string types.
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//
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// Various implementations of this interface are provided:
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// ByteSink:
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// CheckedArrayByteSink Write to a flat array, with bounds checking
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// StringByteSink Write to an STL string
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// This code is a contribution of Google code, and the style used here is
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// a compromise between the original Google code and the ICU coding guidelines.
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// For example, data types are ICU-ified (size_t,int->int32_t),
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// and API comments doxygen-ified, but function names and behavior are
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// as in the original, if possible.
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// Assertion-style error handling, not available in ICU, was changed to
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// parameter "pinning" similar to UnicodeString.
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//
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// In addition, this is only a partial port of the original Google code,
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// limited to what was needed so far. The (nearly) complete original code
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// is in the ICU svn repository at icuhtml/trunk/design/strings/contrib
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// (see ICU ticket 6765, r25517).
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#ifndef __BYTESTREAM_H__
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#define __BYTESTREAM_H__
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/**
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* \file
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* \brief C++ API: Interface for writing bytes, and implementation classes.
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*/
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#include "unicode/utypes.h"
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#if U_SHOW_CPLUSPLUS_API
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#include "unicode/uobject.h"
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#include "unicode/std_string.h"
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U_NAMESPACE_BEGIN
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/**
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* A ByteSink can be filled with bytes.
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* @stable ICU 4.2
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*/
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class U_COMMON_API ByteSink : public UMemory {
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public:
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/**
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* Default constructor.
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* @stable ICU 4.2
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*/
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ByteSink() { }
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/**
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* Virtual destructor.
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* @stable ICU 4.2
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*/
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virtual ~ByteSink();
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/**
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* Append "bytes[0,n-1]" to this.
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* @param bytes the pointer to the bytes
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* @param n the number of bytes; must be non-negative
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* @stable ICU 4.2
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*/
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virtual void Append(const char* bytes, int32_t n) = 0;
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/**
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* Appends n bytes to this. Same as Append().
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* Call AppendU8() with u8"string literals" which are const char * in C++11
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* but const char8_t * in C++20.
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* If the compiler does support char8_t as a distinct type,
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* then an AppendU8() overload for that is defined and will be chosen.
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*
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* @param bytes the pointer to the bytes
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* @param n the number of bytes; must be non-negative
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* @stable ICU 67
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*/
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inline void AppendU8(const char* bytes, int32_t n) {
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Append(bytes, n);
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}
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#if defined(__cpp_char8_t) || defined(U_IN_DOXYGEN)
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/**
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* Appends n bytes to this. Same as Append() but for a const char8_t * pointer.
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* Call AppendU8() with u8"string literals" which are const char * in C++11
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* but const char8_t * in C++20.
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* If the compiler does support char8_t as a distinct type,
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* then this AppendU8() overload for that is defined and will be chosen.
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*
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* @param bytes the pointer to the bytes
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* @param n the number of bytes; must be non-negative
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* @stable ICU 67
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*/
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inline void AppendU8(const char8_t* bytes, int32_t n) {
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Append(reinterpret_cast<const char*>(bytes), n);
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}
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#endif
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/**
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* Returns a writable buffer for appending and writes the buffer's capacity to
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* *result_capacity. Guarantees *result_capacity>=min_capacity.
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* May return a pointer to the caller-owned scratch buffer which must have
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* scratch_capacity>=min_capacity.
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* The returned buffer is only valid until the next operation
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* on this ByteSink.
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*
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* After writing at most *result_capacity bytes, call Append() with the
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* pointer returned from this function and the number of bytes written.
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* Many Append() implementations will avoid copying bytes if this function
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* returned an internal buffer.
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*
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* Partial usage example:
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* int32_t capacity;
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* char* buffer = sink->GetAppendBuffer(..., &capacity);
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* ... Write n bytes into buffer, with n <= capacity.
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* sink->Append(buffer, n);
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* In many implementations, that call to Append will avoid copying bytes.
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*
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* If the ByteSink allocates or reallocates an internal buffer, it should use
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* the desired_capacity_hint if appropriate.
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* If a caller cannot provide a reasonable guess at the desired capacity,
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* it should pass desired_capacity_hint=0.
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*
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* If a non-scratch buffer is returned, the caller may only pass
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* a prefix to it to Append().
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* That is, it is not correct to pass an interior pointer to Append().
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*
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* The default implementation always returns the scratch buffer.
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*
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* @param min_capacity required minimum capacity of the returned buffer;
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* must be non-negative
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* @param desired_capacity_hint desired capacity of the returned buffer;
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* must be non-negative
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* @param scratch default caller-owned buffer
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* @param scratch_capacity capacity of the scratch buffer
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* @param result_capacity pointer to an integer which will be set to the
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* capacity of the returned buffer
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* @return a buffer with *result_capacity>=min_capacity
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* @stable ICU 4.2
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*/
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virtual char* GetAppendBuffer(int32_t min_capacity,
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int32_t desired_capacity_hint,
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char* scratch, int32_t scratch_capacity,
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int32_t* result_capacity);
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/**
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* Flush internal buffers.
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* Some byte sinks use internal buffers or provide buffering
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* and require calling Flush() at the end of the stream.
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* The ByteSink should be ready for further Append() calls after Flush().
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* The default implementation of Flush() does nothing.
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* @stable ICU 4.2
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*/
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virtual void Flush();
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private:
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ByteSink(const ByteSink &) = delete;
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ByteSink &operator=(const ByteSink &) = delete;
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};
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// -------------------------------------------------------------
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// Some standard implementations
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/**
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* Implementation of ByteSink that writes to a flat byte array,
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* with bounds-checking:
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* This sink will not write more than capacity bytes to outbuf.
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* If more than capacity bytes are Append()ed, then excess bytes are ignored,
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* and Overflowed() will return true.
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* Overflow does not cause a runtime error.
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* @stable ICU 4.2
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*/
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class U_COMMON_API CheckedArrayByteSink : public ByteSink {
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public:
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/**
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* Constructs a ByteSink that will write to outbuf[0..capacity-1].
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* @param outbuf buffer to write to
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* @param capacity size of the buffer
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* @stable ICU 4.2
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*/
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CheckedArrayByteSink(char* outbuf, int32_t capacity);
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/**
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* Destructor.
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* @stable ICU 4.2
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*/
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virtual ~CheckedArrayByteSink();
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/**
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* Returns the sink to its original state, without modifying the buffer.
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* Useful for reusing both the buffer and the sink for multiple streams.
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* Resets the state to NumberOfBytesWritten()=NumberOfBytesAppended()=0
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* and Overflowed()=false.
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* @return *this
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* @stable ICU 4.6
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*/
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virtual CheckedArrayByteSink& Reset();
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/**
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* Append "bytes[0,n-1]" to this.
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* @param bytes the pointer to the bytes
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* @param n the number of bytes; must be non-negative
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* @stable ICU 4.2
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*/
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virtual void Append(const char* bytes, int32_t n);
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/**
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* Returns a writable buffer for appending and writes the buffer's capacity to
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* *result_capacity. For details see the base class documentation.
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* @param min_capacity required minimum capacity of the returned buffer;
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* must be non-negative
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* @param desired_capacity_hint desired capacity of the returned buffer;
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* must be non-negative
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* @param scratch default caller-owned buffer
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* @param scratch_capacity capacity of the scratch buffer
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* @param result_capacity pointer to an integer which will be set to the
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* capacity of the returned buffer
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* @return a buffer with *result_capacity>=min_capacity
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* @stable ICU 4.2
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*/
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virtual char* GetAppendBuffer(int32_t min_capacity,
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int32_t desired_capacity_hint,
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char* scratch, int32_t scratch_capacity,
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int32_t* result_capacity);
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/**
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* Returns the number of bytes actually written to the sink.
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* @return number of bytes written to the buffer
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* @stable ICU 4.2
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*/
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int32_t NumberOfBytesWritten() const { return size_; }
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/**
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* Returns true if any bytes were discarded, i.e., if there was an
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* attempt to write more than 'capacity' bytes.
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* @return true if more than 'capacity' bytes were Append()ed
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* @stable ICU 4.2
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*/
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UBool Overflowed() const { return overflowed_; }
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/**
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* Returns the number of bytes appended to the sink.
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* If Overflowed() then NumberOfBytesAppended()>NumberOfBytesWritten()
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* else they return the same number.
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* @return number of bytes written to the buffer
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* @stable ICU 4.6
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*/
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int32_t NumberOfBytesAppended() const { return appended_; }
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private:
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char* outbuf_;
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const int32_t capacity_;
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int32_t size_;
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int32_t appended_;
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UBool overflowed_;
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CheckedArrayByteSink() = delete;
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CheckedArrayByteSink(const CheckedArrayByteSink &) = delete;
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CheckedArrayByteSink &operator=(const CheckedArrayByteSink &) = delete;
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};
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/**
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* Implementation of ByteSink that writes to a "string".
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* The StringClass is usually instantiated with a std::string.
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* @stable ICU 4.2
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*/
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template<typename StringClass>
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class StringByteSink : public ByteSink {
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public:
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/**
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* Constructs a ByteSink that will append bytes to the dest string.
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* @param dest pointer to string object to append to
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* @stable ICU 4.2
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*/
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StringByteSink(StringClass* dest) : dest_(dest) { }
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/**
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* Constructs a ByteSink that reserves append capacity and will append bytes to the dest string.
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*
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* @param dest pointer to string object to append to
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* @param initialAppendCapacity capacity beyond dest->length() to be reserve()d
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* @stable ICU 60
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*/
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StringByteSink(StringClass* dest, int32_t initialAppendCapacity) : dest_(dest) {
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if (initialAppendCapacity > 0 &&
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(uint32_t)initialAppendCapacity > (dest->capacity() - dest->length())) {
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dest->reserve(dest->length() + initialAppendCapacity);
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}
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}
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/**
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* Append "bytes[0,n-1]" to this.
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* @param data the pointer to the bytes
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* @param n the number of bytes; must be non-negative
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* @stable ICU 4.2
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*/
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virtual void Append(const char* data, int32_t n) { dest_->append(data, n); }
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private:
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StringClass* dest_;
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StringByteSink() = delete;
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StringByteSink(const StringByteSink &) = delete;
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StringByteSink &operator=(const StringByteSink &) = delete;
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};
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U_NAMESPACE_END
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#endif /* U_SHOW_CPLUSPLUS_API */
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#endif // __BYTESTREAM_H__
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